Automatic telephone system.



A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT.9- I912.

Patented Sept. 14, 1915. I

SHEETS-SHEET I A. H. DYSQN. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT. 9. 1912.

Patented Sept. 14, 1915.

3 SHEETSSHEET 2 r .E RR k H. vsou. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT. 9 I912.

Patented Sept. 14, 1915.

SHEETS-SHEET 3. I ("F fizz/5271272.- 555-5577275022.

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l .annimin i1. bison, or rena n. in, ASSIGEYGRTG amass swircnnoannistnnSUPPLY oomanfnjoa carcass; ILLINOIS, a conwonatrron on rumors 1y)" Be"tlni wnfthat I, ALF ED Dyson, a

citizenef tile-United States at America, my siding in NeivfYork, countyofNew York,

and St ate of New ,York,have inyented certain new and usefulImprovements in Auto.- matic Telephone Systems, of which the fol lowingis a specification.

My invention relates in general to telephone systems n Which automaticswitches {-iare employed for extending connections of callin telephonevlines and inthe'preferred I 1 embo iznent'of my invention, as hereindisclosed, I preferalglye'mploy switches or the twoedim'ension that issi vitches having bank contact diy ide'd into groups and assoa-seconda'iQ seems toreceive a primary select a gr'oup and thereafter y ustment toselect a contact 1115a igroup. The -pre ferred type. 01 sw tch- 4 ciatedWiper adjustmen to 1 q e iiploy'ed dces "not include a release magnet 1but therelease of the wipers; is effected by continuing thesecondary-travel thereof until they have advanced beyond the lastcontact master switches for starting m en line so I line.

of the selected group whereby they are automatieally restored by springtension. These switches may be referred to as of the two- 'dimensio'nstep ahead release type. In the preferred embodiment ofv my invention Ialso use linesejlector switches ADKlflSSOClZlbQG lector to seekconnection with the calling Certain; features of myfinvention relatemore particularly to an improved circuit'anfi rangemehtgof the linesome; and .Inaster Another feature is the provision "of means fo-automatically cutting the secondary magnet when, in its releaseoperation, it has stepped the wipers beyond the lost contact of the row.

Other ieatures'of my invention will be u more particularly pointed outin the specification and the appended claims.

For a more complete understanding of my invention reference will be madeto the aocompanying' drawings, in Which o s s l igure i comprising pantsl,2-, and 3 lllllS- trates diagrammat c-a1ly automatic telephone systemand'Fig. 2 is aperspecti've view of the contact bank and Wiper arrange-.ment. l

' Referring now more particularlyto tlm system of. Fig, 1', by placingpart 2 to the right of newsman sarcasm.

dom tics of Letters Patent. yatented. Sept. 1915. I

9, 191a sea in. fiasco. Y

. nccted to terminals of 10 line selectors C so that each line selectorC has access to any one of its group of 100 lines. In the illustrationbut two such multiple connections are shown. For each such group of 100lines and 10 associated. line selectors, a common master switch D isprovided being adapted upon initiation of a call over one of theassociated lines to start an idle line selector C toseek connection withthe calling line. A first selector E is connected to each line selectorC so that it may be operated b the calling subscriberto extend thecircuit of the calling line. 1000 second selectors F are provided and1000 connectors G are also provided these being distributed and multiledin a Well known manner. Substation i line L and line circuit B of Fig. 1part 1 3 represent a called-for substation and asso- =ciated circuits. T

Selectorand connector switch comtruw thaw-Before proceeding further Withthe description of the circuits, it is believedkthat their operationwill be more readily understood by referring to llilGf-iZYPG of selectorand connector switchmechanism preferably used. a w

For use with the selector and connector circuits of the system of Fig.1, a switch such is shown in an application of VViL liani Kaisling for.automatic switch for telephone systems, Serial No. 600,664, Pat

No 1,131,140, filed lanuary 3, 1911, may he i I paragraph, in generalcomprises :a bank of conta cts made up of 100 sets of contacts withthree contacts 0, 10, 11, to each set, and divided into ten groups often contact sets {each es illustrated. diagrammatically in Fi I fa ofwipers 5, '7, 8, are provided,to cooperate T'Cltll the bank contacts,- aprimary magnet (comespondlng M. of the switch circuits) being adapted toprimarily adjust the wipers through the medium of a primary shaft PS toselect a group of contacts, and a secondary magnet (corresponding to S.M. of the switch circuits) is pro vided to step the wipers through themedium of a secondary shaft SS in a secondary direction in a plane atright angles to the primary, to select a contact set of the selected subgroup. The switch construction is such that the wipers are advancedagainst the tension of a" pair of so-called watch springs, one springopposing each movement respectively.

To release the wipers, that is, to restore them to normal, the secondarymagnet is again actuated to step the wipers beyond receiver.

the last contact of the. sub group whereby they are auton'iaticallyrestored to normal by the springs referred to, but over a different paththan that taken by the wipers in the advance movement of the switchinselecting a contact. Thus, in the operation of the switch the contact nends of the wipers travel in a primary direction to select a sub groupof contacts, then in a secondary direction to select a contact in thesub group, and in the release of the wipers this secondary travel iscontinued until the contacting ends have passed beyond the last contactin the group, whereby they are automatically released to continue theirrestoration to normal, this continued movement 'being in a, planeparallel to the primary movement but in an opposite direction until theyreach a point directly above the starting point when they are moveddownward through a plane parallel to the secondary movement, but in adirection opposite to the secondary movement, until they reach theirnormal starting point. A complete travel of the wipers is indicated bythe dotted line in Fig. 2.

A set of primary off-normal spring contacts ION are moved upon'the firstprimary step of the switch while a set of secondary off-normal springcontacts SON are moved upon the first secondary step of the switch. Itis to be understood that for a more complete. understanding of thisswitch, reference is to be had to the above identified application.

Each substation comprises preferably a well known form of switch hookand receiver, a call bell and condenser normally bridged across the linewhich are adapted to have their circuit interrupted and. the circuit ofa transmitter and. impedance coil bridged across the line upon removalof the A calling device 1 is also provided con'iprising'a toothed dialmember 2 adapted to cooperate with impulse springs 3 in such a mannerthat when the dial is adare not interrupted but its spring, contacts 3are interrupted according to. the number of teeth on dial v2 which wereinitially advanced.

Substation A is connected to the central oflice by means of a pair ofline limbs 4, 5 terminating in a line circuit B comprising preferablv aline relay LR and cut-ofi' relay CO. Line relay LR is adapted to beenergized u )011 initiation of a call 'over its'associate line to startan idle lineselector C and upon connection being made with" the callingline by s'uchline selector, cut-off relay CO is energized to extend thecalling line circuit and interrupt the circuit of the line relay LR.

As previously referred to, thelines are divided into groups of 100 eachand these groups are further divided into 10 sub groups of 10 lineseach, corres ionding to the 10 groups J J J etc., of contacts of theline selector such as illustrated in Fig. 2. In starting a line selectorC to select a calling line, its wipers such as 6, 7, 8, are firstoperated to pick out the group of, line contacts 9, 10, 11, whichinclude the contacts of the calling line and for each such group of linecontacts or terminals 9, 10, 11,

a pair of group contacts, 12, 13 are proe.

line as L is calling, the associated group relay GR is energized toren'iove ground from the associated group contact 12 so the lineselector C in seeking the calling line stops its wipers in their primarymovement upon reaching the ungroluuled contact 12.

Master switch I) .Common to each group of 100 lines is a master switchl) which is preferably a simple rotary switch COIIIPI'lS- ing two setsof contacts 16 and 17 and cooperating wipers 18 and 19, said \vipersbeing'insulatingly mounted upon a, common shaft adapted to be rotated bymeans of a suitable ratchet or pawl arrangement driven by a motor magnetM. As previously stated I preferably employ 10 line selectors C for eachgroup of 100 lines and therefore I provide as many contact sets 16, 17(in this case 10 sets), its there are line selectors C. Intermediatecontacts 16, 1 1 are pFovjdr-d to prevent starting two line selectorsaftera Master switch I) is so arranged with respect to line circuits B,and line selector 0,

that should tliere be more than one line simultaneously callingt masterswitch I) starts an idle line selector G and upon the first step of suchswitch C,'master switch D advances to the nextfidle set of C(ultatwSandstarts an 25), lectors' other line switch C and so on according tothe number of lines culling. The starting is clificrentielly connectedand when a circuit is closed through its winding 27 and LR in series,contac 36 is closed, and when relay RR of C is connected. in series withill rel after the calling line, a differential effect is }'rrodifced,"causing the interruption of contact egiudings otLl't u'iid B121 s are soreluted to w ndings 27, 22 of STflthat when thc two series circuits asabove re-' terre'cl'to are closed, the magnetic action of windings 27heutralise each other. it several are simultaneously calling, therewould be more than one relay L R'co'nnccted ii] series with winding 27,and therefore the starting relay is not neutralized J to ones. "'t 36utitil us many line'se 5C3 ecu started as there are lines will hedescribed more in de- -'scZccf07' C.--E 1Cl1 line selector C :1 y PS3and secondary selecting respectively. A release relay RR providedpreferably of: the slow acttl rim ry otf-uormal. contacts iderycit-normal. contacts SQN, ems overrunw'aoutacts (ill are also provided,being operated as pointed out in connection with Fl i A First Iscccoriill-"T'Cl llQ first selectors E mary and secondary magnets ill/irespectively (lit-normal and ever-run switch contacts, iOllk SIGN 0B 22s also provided'these being indicated by fliers-rice characterscorresponding to the reference chors indicating like parts at iiueselector 3. 'y or impulse relay hridged across the, d to he energizedling line. A main l :e' relay is s so provided being slim zmtiug typeand adapted to he cu cruised. responsive to relay and maintained ergized until. ngecl deemm of relay lil e i, which co on receiver isr w?Perl utthe colln stul'ion. socollec. comlery relay o is also controlledh .3 1y PR and is ed to cited; as, -iy circuit change u-h set of priceimpulses have been 1 by impulse relay l li. Test controlsuiugg'nett'ihil when opswitch to select an idle of 21 causing; itrehearse of the mm otiiormal :tor already re 51;, corresponding w th thesui'lix 2 relay S'W which is operated after the first winding 22 whichoccurs when switch s s-ct of primary impulses to disconnect the primarymagnet and connect the secondary magnet in circuit, a line test relay LTwhich is initially energized responsive to the secondsecoudury circuitchange tra'nsm'itted to switch G, to test the terminals of thecalledline to determine their idle or busy condi- 'tion. A .so-calledringing relay BI is also provided, a tip relay TIP which is actuated 30upon response of thecalled subscriber, a circuit closing relay CLenergized after the called subscriber has answered to close the circuitbetween the calling and. called lines,

a busy back'apparatus BB and ringiugap pzu'etus R. The culled substationH is connected to a line-L and a line circuit B similar to the linecircuit B. Y

O erutiML-J'Xaving "described in generalso' the apparatus involved incsts ilishing a connection, the operation of thsystem in establishing aconnection betwr o a calling and called substation will now described:Assuming a-subscribcr at A flcsires'to connect with a subscriber atsulistution H whose. telephone number is 3456, he will remove hisreceiver from its switch-hook whereby a circuit for line relay LR- isestablished traced trou'i battery through the winding of LR, normalcoiuuct 520, line conductor 5 substation A, line conductorl and normalcontact 21 to ground. Relay LR is thus energized and a series circuitincluding its winding and winding 27 of the difi'crentiul start-ing lOSrelay ST (muster switch D.) is established traced through Lil, alternatecontact 24, normal contact 25, common conductor 26 and the winding 2'7to ground. Starting relay ST therefore energized over the path tracedand the relays'S'l and LR remaiu energized over szlid series circuit. IThe clos' ing alternate contact 28 of relay LR couuects a ground or busypotential to the testv contacts 29 to prevent any connector switch fromcoimecting to the terminals 29, 30, 31, of the line oi 'substutiou A.Responsive to the closing of' alternutecontuct 32 of relay Lit circuitthrough winding 33 of group 4 relay GR is .established throughresistance 34, energizing relay GR and causing interruption of itsContact to remove ground from its group contact l2. Responsive toeuerg'ization of relay ST its alternate contact 86 is closedestablishing a circuit for advaiioing relay AR, traced front ground atalternate contact 36, Wiper 18, contact 16 common 47, contact 17 Wiperl9 anclthe winding 01' AH to battery. Relay AR therefore closes itselteruete coutuct. fiycausing M to advance the wipers one step. If thecontacts 16, 17, thus engaged lead to an idle pair of switches C E, testcontact 17 is on open circuit, and relay AR de'energizes ren- 5 deringthe wipers inert. A starting circuit for the idle line selector 0 istherefore established traced from ground through alternate contact 36,wiper 18, contact 16, conductor 37, normal contact 38 and the winding ofPSR to battery. This ground connection over conductor 37 also extendsthrough normal contact 39 and the winding of release relay HR tobattery, causing its energization. Alternate contact 10 of relay 5 HR isthereby closed connecting the winding of relay RR in circuit withwinding 22 of relay ST, (master switch D) this circuit being traced frombattery through the winding of RR, alternate contact 4.0, normal con 3tact 41, conductor 42 and winding 22 to ground. If at this time no otherline in the group of master switch D is calling, due to the equal flowof current through windings 22, 27 of differential relay ST, itsarmature I 25 is retracted interrupting alternate contact 36. It will beremembered that the circuit through winding 27 included the winding ofrelay LR- and as the resistance of the winding of LB is substantiallythe same as the 1e- 80 sistance of RR, it will be apparent that thedifferential effect upon relay ST causes its armature to retract. Ofcourse if any other line or lines of the group of master switch D becalling at this time, due to the greater now of current through winding27, contact 36 will be maintained closed in order to start another lineselector when master switch D is advanced as will be described.

Referring again to line switch 0 it will be 40 remembered that primaryselecting relay PSR is energized. Therefore its alternate contact 43 isclosed establishing an operating circuit for primary magnet PM wherebythe wipers 14, 15 of switch C are advanced 45 to the first groupcontacts 12, 13, respectively, while wipers 6, 7, 8, are advancedopposite the first row or group of contacts 9, 10, 11. I have indicatedthe line of substation A as being associated with the third sub group oflines, and assuming no other line. is calling at this time, the firsttwo sub group contacts 12 are at a ground potential as indicated. forrelay PSR is established through its alternate contact 44. Magnet PMtherefore advances thewipers another step and finding the second groupcontact 12 also grounded the wipers are advanced another step, andcontact 12 of this third sub group being un- 60 grounded the circuit forrelay PSR is interrupted allowing it to deenergize and interrupt thecircuit for magnet PM. Upon the first primar' step of switch C, contactsPON are move to their alternate position 6' and due to the closing ofalternate contact Therefore a locking circuit 45, ground is connected tocontact 17, wiper 19, and the winding of advancing relay AR to battery,causing its 'energization whereby alternate contact 46 is closedestablishing a circuit for motor magnet M which advances wipers 18, 19,a single step. If at this time no other line in the group is calling,starting relay ST has its contact 36 interrupted as described andtherefore relay AR deenergizes and the wipers 18, 19 remain inert. If onthe other hand, some other line in the group also be calling, alternatecontact 36 of starting relay ST is closed (due to the preponderance ofcurrent in winding 27) and due to said single step of wipers 18, 19, goa circuit from ground at; alternate contact 36 is established throughwiper 18, contact 16 conductor 47, contact 17 wiper 19 and the windingof AR to battery maintaining said relay energized, and the wipers are 35advanced another step. Assuming the contacts 16, 17 now engaged lead toan idle selector C, relay AR deenergizes interrupting the circuit for Mand rendering wipers 18,

19 inert. As soon as wiper 18 engaged the 0 contact 16 leading to suchan idle line selector O, with starting relay ST energized, (due toanother calling line) a starting circuit for such an idle lme selector Cwill be established whereby it will be started from 5 normal to seekthis second calling line. Thus it will be apparent should more than oneline be calling at one time, as soon as one line selector 0 makes astep, a second switch will be started and upon the second switch makinga step a third switch will be started and so on until as many lineselectors C have been started as there are SilllllltflIlQOllS calls upto the number of line selectors C" consigned to the group.

Referring again to relay PSR, upon its deenergization when the callinggroup is reached as pr viously referred to, a circuit for secondaryselecting relay SSR is establ lished from ground through normal contact43 of PSB alternate contact 48, conductelr 49, normal contact 50, andthe winding of SSR to battery causing the energization of the said relaySSR whereby its alternate contact 51 is closed establishing an oper-'ating circuit for magnet SM. Magnet SM therefore steps wipers 6, 7, 8,in a secondary direction to engage the first set of contacts 9, 10, 11,in the selected sub group. \Vith a line circuit at normal, its testcontact 9 is connected to ground through normal contacts 52, 32, butwhile a line is calling, due to the interruption of normal contact 32,test contacts 9 thereof are on open circuit and upon a calling'linebeing selected its 12:, test contacts 9 are again connected to ground-pote-ntial as will be more clearly pointed out. From this it will beseenthat only during the period between initiation of a call and until alme is selected are its test l g. contacts 9 selectable. 'ilherefore, ifthe first test contact 9 connected with is associatec with a line whichis not calling, or has already been connected with, it will be connectedto ground and therefore a locking circuit for relay SSH is establishedtraced' frcm the said contact 9, wiper 6, normal contact :23, alternatecontact 54 and the winding of SSR to battery maintaining said relayenergized. Magnet SM therefore advances the Wipers another step and infact continues I to do so until Wiper 6 reaches an ungrounded testcontact 9 whereby the circuit for relay SSR is interrupted causing it todeenergizeand interrupt'the circuit. for magnet SM whereby wipers 6, 7,8, reinain in engage ment with the terminals 9, 10, 11, of the cal ingline. I

Referring again to relay SSE, upon its s'aid initial energization itsalternate contacts 55 and 56 are closed thereby connecting the winding57 of relay PR in series with Winding 58 of group relay GR, and thelower winding 59 of relay PR in series with winding 22 of starting relayST; The circhit including winding 57 of relay PR and winding 515 of GRis traced from ground through the winding 57, primaryv conductor P.alternate contact 55, normal contact 60,

"' wiper 15 contacts 13, and winding 58 to battery. It will be notedthat the initial energizing circuit for relay GR includes resistance 34and the windings of relay GR are preferably proportioned so that whenwinding 57 of relay PR {which is substantially the same resistance asresistance 34) is connected in series with the winding 58 of relay GR,due to the differential effect produced,

relay GR retracts its armature closing normal contact and thereby againconnecting ground to group contacts 12 rendering the associated group"of contacts 9, 10, ii, unselectable. Thus, it will be seen that as soonthe secondary selecting relay SSH is energized to close the circuit forse ondary mag-net SM, group -relay GR deenergizes to again ground itsgroup contact 12 so that if some line in a sub group beyond sub group 12is calling and another line selector C is started, such selector canpass all sub group contacts 12 to reach the subgroup of the othercalling line. Of course if some other line in the sub group of line Aisals'o calling at this time, a circuit through its re-' sistance 34 andwinding 33 of GR is sufficient to maintain the armature of relay GRattracted, so that when the other .Ffi'f-ll'llQl lf line switch Creaches the sub group cunt-act 12 in which the line of substation A andthis other calling line is located its movement will be stopped in amanner similar to that described inconnection with line selector C. Alsoupon the first secondary step of lineselector C, secondary of normalcontact 4-1 'is interrupted' whereby the starting relay I I i l I I I Vi} 0 ST has its finding-22 connected in series circuit with the windmg59 of relayvPR, this circult being *traced from. battery through saidwinding 59, secondary conductor S, alternate contact 56, normal contact(Sh-conductor i2 and winding 22 to ground maintaining relay STneutralized and its contact 36 interrupted until the line has beenselected. Upon wipers 6, 7, 8, reaching the terminals 9, 10, 11, of thecalling line, there being nowground upon test contact 9 the circuitforrelay SSR is interrupted whereb it de'e'ner izes renderin ma net SMinert and due to the interruption of the alternate contacts 55,56,'the'c1rcu1t from windings 57, 59 of relay PR through windings 58 and22 of relays ST and GR respeotirely are' interrupted. After the circuitthrough winding 22 is interrupted by contact56 as stated, the circuitthrough winding 27 is momentarily maintained closed thereafter becauserelay CG does not interrupt its contact 25 until after contact 56interrupts, but I have found th s 'doesnot "cause sufficient attractionof the armature of ST to close alternate contact 36. Therefore wipers18, 19 remain in engagement with contact 16 17 until another call.

Referring again to relay SSR, upon its de- ,ii 9, wiper 6, normalcontacts 23 and 54:

to ground. This ground connection is also effective to maintain a busy'jpotential upon' the multiple test terminals 9. Due to the interruptionof normal contact 25 of CO, the series circuit including line relay LRand winding27 of relay ST is interrupted, causing dc'e'nergization ofLB. Upon said re' storation of relay LR its alteriiate'contact 32 isinterrupted,thereby interrupting the on;-

. cuit through winding 33 0f GB, and as the circuit through winding 58thereof was interrupted due to the interruption of alternate contact 55when relay SSE de' nergized,

"relay GR keeps its armature retracted thereby maintaining its sub groupcontact 12unselectable. Should anotherline in the same sub group asline; L be calling, there would be a preponderance of, current throughwinding 33 of relay GR and therefore its armature would remainattracted, and its group contact 12 selectable-until this other saidline is selected, and its relay LRdeenergized? Referring to relay- RR itwill be remem normal -ground. Upon'the hrst secondary step of bered thatit was initially energized by a circuit from grounded contact 36 ofrelay ST and then established 'a locking circuit for itself through itsalternate contact 40, contact 41, and winding 22 to switch C, secondaryoti' normal contact 41 is interrupted and alternate contact 41 closed,and as relay PR was energized responsive to the initial energization ofrelay SSR, due to the closing of alternate contact 41 a substitutelocking circuit for relay RR was established over conductor 63 to groundat alternate contact (34, of PR. Relay RR being a slow acting relay doesnot retract its armature until a prolonged interruption of saidalternate contact (H. That is, while relay PR is vibrating to transmitprimary impulses, the rapid interruptions of alternate contact 64 do notallow retraction of the armature of relay RR, but when the receiver isreplaced, a prolonged de't nergization of PR allows relay HR- torestore. Upon said energization of cut-off relay CO,

due to the closure of its alternate contact. 20,

impulse relay PR is maintained energized by a circuit over the callingline, this circuit being traced from ground through winding 57 of relayPR, primary conductor P to line conductor 5, substation A, lineconductor 4, secondary conductor Sthrough winding 59 of relay PR tobattery.

The circuit of the calling line having been extended to first selectorE, the subscriber at A- operates dial 1 to cause three interruptions ofcontacts 3, corresponding to the first digit of the called substationnumber. these interrul')tions causing three interruptions of themetallic energizing circuit of relay IR whereby it retracts its armaturethree times causing three operations of its contact sprin s. Relays RRand MRR be ing slow acting relays do not retract their armaturesresponsive to these rapid interruptions of alternate contact til. Uponthe first closure of normal contact 65 of relay PR, a circuit for slowacting secondary relay SR- is established, causing its energization anddue to the ensuing impulses through said nm'mal contact (55, maintainingits armature. attracted until the cessation of the primary operations ofrelay lR. These impulses tiow from battery through SR, normal contact6;") to ground, at alternate contact (3T. Responsive to the threeclosures of normal contact 66 of relay PR, three primary impulses aretransmitted through primary magnet PM, traced from ground at alternatecontact (37, normal contact 66,

primary conductor 1", conductor 68, normal contact. (39, and the windingof PM to battery, causing three operations thereof. This etl'ects threesteps of wipers (39, 70, 71 to select the third row of contacts 713, T3,T4 which 'rolm leads to second selectors ll havswitches C E unselectablewhile switch East 75 ott-normal.

Following the said three operations of relay PR a prolonged energizationthereof follows, that is it remains energized until the next operationof the calling device, and therefore, due to the prolonged interruptionof normal contact 65 secondary relay SR is dei nergized to allow itsarmature to retract, whereby normal contact T7 is closed establishing asecondary circuit change to effect the energization of test relay TR.This circuit is traced from battery through the winding of TR, normalcontact T8 of SON, alternate contacts T9, TT. impedance coil 80,alternate contacts (5'5, 6T to ground. Respoln sive to said energizationof TR its alternate contact 81 is closed establishing a circuit for thesecondary magnet SM whereby magnet SM advances wipers (it), T0, T1 intoengagement with the first set of contacts T2, T3, Tl in the selectedgroup. ()n the first secondary step of the switch. the secondaryoff-normal contact T is interrupted. thereby interrupting the initialenergizingcircuit for test relay TR which now becomes dependent forfurther energization upon a circuit extending through alternate contacts32, H3, wiper ti and the [irst encountered Lest contact T2 which it busyhas a ground or busy poten tial connected thereto. as will be pointedout. Assuming this tirst encountered set is busy, relay Th is maintainedenergized and there fore magnet SM advances the wipers another step andin tact continues such advancement as long as its wiper 9 is in engaging busy test contacts TL. t'pon the test wiper ti! engagin testcontact T2 of the idle second selector 1. the circuit for relay TR isinterrupted whereby it decnergizes interrupting the circuit for magnetSM and rendering wipers tit), T0. Tl inert. Also upon decnergization ofrelay TR. due to the closing of its normal contact 52. ground isconnected to wiper (it) and the multiple test terlninals T2 of theselected switch 1*. thereby rendering it unselectable by any otherswitch. It will be noted that during the secondary operation of switchI) ,while its wipers are passing over bank contacts. due to theinterruption of normal contacts 35, and $6, line wipers T0 and Tl aredisconnected so they will not interfere with any existing connections.

As the next step in establishing the coilnection, the subscriberoperates calling de masters;

1 vice 1 to cause four interruptions of its contact springsS,corresponding to the second digit in the called substation number, thereby interrupting the circuit of relay PR four times, causing fouroperations of its contact springs. Responsive to the firstclosure of itsnormal contact 65, secondary relay SR is again energized and maintainedenergized hile relay PR is operating. Responsive to the four closures ofnormal contact 66, four impulses of current are transmitted throughprimary magnet- PM of second selector being traced from ground atalterpate contact (37, normal contact (36, primary conductor P normalcontact 85, wiper 70, contact 73, primary conductor l, normal contact-87and the winding of PM? to battery causing, four operations thereof. Thefirst one of these four primary impulses also follows a path fromconductor P over conductor 88, primary off-normal. contact 88, normalcontact 89 and the winding of release relay RR to battery, causing itsenergization whereby its alternatecontact 89 is closed establishing alocking circuit to the grounded test contact 72, so that release relayRIF is new controlled from-first selector E, Responsive to the said fouroperations; of magnet Pll/P, wipers 90, 91, 92, are advanced four'stepsto select the fourth sub group of contacts 93, 95 which arefthe subgroup contacts leading to connectors in the fourth hundred group, Which.group includes the line I of calledsubstation H. Upon cessation of thesaid primary operations of relay PR, secondary relay SRretracts itsarmature as be fore, effecting another secondary circuit change wherebyan energizing circuit for test relay T R is established, traced from/the medium of main release relay MRR as groundover the previouslydescribed circuit through normal contact 77 of relay 5R, then overconductor S}, normal contact 8.6, wiper 71, contact 74', alternatecontact 96,'normal i contact 97, conductor 98 and the winding of TR tobattery. .Its alternate contact 99 is therefore closed, establishing anoperating of called substation ll.

circuit for secondary magnet 8M whereby Wipers 90, 91, 92 are steppedinto engagement with the first set of contacts 93, 94, Q5.

Idle sets of contacts 93, 94, 95, have their test contact 93v preferablyon open circuit,

while such contact sets wheirbusy have their test contact 93 connectedto the busy or; ground potential as'will appearfromthe following.Therefore when the initial ener "izin circuit for relay TR isinterrupted at b h Y '1 normal contact 9 of bON", upon the firstsecondary step of switch F, relay TR being connected through itsalternate contact 100 and alternate contact 101 to test wlper 90, ismaintained energized (assuming the first test contact 93 is busy) sothat magnet SM" continues to advance the wipers until an idle set ofcontacts J3, 9i, and 95 is reached.

Upon engaging such an idle set of contacts which we will assume are thecontacts lead ing to switch G illustrated, relay 'llR deenergizedinterrupting the circuit for magnormal contacts 102,103, line wipers 91,92,

are on open circuitsothat there is no interference with any existingconnections they might engage.

The calling line has now been extended to connector G, and thesubscriber at substation d operates calling device 1 to cause 5interruptions of its contacts 3, corresponding to the third digit of thecalled substation number, thereby eiiecting live interruptions of thecircuit of primary relay PR and causing fire operations of its contactsprings. Responsive to these operations secondary relay SR is energizedand maintained energized in a manner as previously described and'due tothe five closures of normal contact 66 of relayPli. the primary impulsesare transmitted over primary conductor 13;, P, P, conductor 10%, normalcontact 105, normal contact 106, and the winding of PM to battery. Thefirst one of the last said series of primary impulses divides atconductor 10? of connector G, following a path through normal contacts108. 109. and the winding of release relay RR to battery causing itsenergization. Its alternate contact 19.9 is therefore closedestablishingz a locking circuit for itself traced over conductor-110,normal contact 111 to grounded test contact 93. Thus release rewill bemoreparticularly pointed out.

Responsive to the five operations of primary magnet PM, wipers 112, 113,ill, are advanced five steps to select the fifth. sub group of contacts115,115. ill. which is'the subgroup including terminals of the lineFollowing the last said series of live primary operations of relay PR,relay SR dci nergizes as before, etl'ecting a secondary circuitchanirewhereby ground is connected to secondary conductor 0, S S, conductor 11alternate contact 119 (which is now closed normal contact 1:20 and thewinding: of switching relay SlV to battery, causing its energ'ixation.lts alternate contact- 1220 is therefore closed establishing a lockingcircuit for relay S r to ground at alternate contact 121. The operationof switching relay Sil disconnects primary magnet PM from the primaryconductor P, and connects secondary magnet 5M thereto, so that the finalset of primary impulses are etiective to operate said n'iagnct SM.

The calling subscriber again actuates calling device 1, to effect sixoperations of contact springs 3 whereby relay PR is operated 6 times topermit 6 primary impulses over the primary conductor'to connector switchG, while the closing of alternate contact (35 effects energization ofsecondary relay SR as before. The said 6 primary impulses flow over thepreviously described path along the primary conductor and then tocontact spring 106, through the alternate contact thereof and theWinding of secondary magnet SM to battery causing 6 operations of SM?This operation steps wipers 112, 113, 111, to the sixth set of contacts115, 116, 117 of the row, which are the terminals of the called line.Following the said 6 primary operations of relay PR, secondary relay SRdeiinergizes as before transmitting a secondary impulse over thesecondary conductor to connector switch G, conductor 122, alternatecontact SON, normal contact 123, and winding 121 of line test relay LRto battery causing the energization thereof. Up .to this point theoperation of the system. is the same whether wipers 112, 113, 114, haveconnected to the terminals of an idle or a busy line. If the called-lineis busy, upon connecting, to its terminals, relay LT is energized and acharacteristic busy signal from busy back BB is transmitted tothecalling subscriber, but if on the other hand terminals of the calledline are idle, relay LT retracts and ringing current applied to theterminals of the called line.

alle/l Um; Mia-Assuming now that the called line is idle, its testterminal 115 has no busy potential connected thereto so that no lockingcircuit for relay LT is established and therefore immediatelydeiinergizes as. will be described. the closing of alternate contact 125of relay Ill at-the said cnergization thereof, a circuit f r thedisconnect relay DR is established from battery thrcngh the windingthereof, alternate contact 125, conductor 126, to ground at alternatecontact 121. Relay DH is therefore energized and its alternate contact127 is closed establishing a direct locking circuit to groundedalternate contact 121. The interruption of normal contact 123 of relayDR interrupts the circuit for line test relay LT which thereforedeenergizes, while the opening of contact 105 disconnects the operatingmagnet from the primary conductor.

Responsive to the closing of alternate contact 128 of relay DR,and-normal contact 129 of'LT, ringing control relay RC is connected inseries with cut-otf relay (10, this circuit being established fromground through the winding of RF, alternate contact 128, normal contact129, wiper 112, contact 11.5, normal contact 28 and the winding of CO tobattery, causing the energi- Responsivi ,o

ing relay BI is periodically energized to operate its contact 133.

Interrupter wheels 180 and 131 are preferably arranged upon a commonSllilftjll the relation illustrated, so that while ringing relay RI isenergized and its alternate.

contact 133 closed, the ringing segment 131"] is connecting ringinggenerator RG to the terminals of the called line, and before the circuitof relay RI is interrupted by interrupter wheel 130, the groundedsection 134 is connected to alternate contact 133 momentarily. Thismomentary application of direct ground is to prevent kicking up of tiprelay TIP from the discharge of ringing current from the called lineconductors, after each application of ringing current. Upon eachdeenergization of relay RI, due to the closing of its normal contact133, tip relay TIP, and impedance coil 135, and a source of battery areconnected in bridged circuit of the called line to be energized uponrespouse of the called subscriber.

Responsive to each application of ringing current to the called line,the call bell at substation H is operated over a circuit traced fromringing generator RG, segment 134 alternate contact 133, wiper 114,terminal 117, line conductor 4, the call bell and condenser atsubstation I-I, co ductor 5, termi-' 'nal 116, wiper 113, conductor 137,alternat contact 138, impedance coil 135 and battery to ground.

The called subscriber in response to the call removes the receiver atsubstation II. from its switch-hook, thereby providing a direct currentpath, and upon the immedr ately followingclosurc ofnormal contact 133 ofRI, (if it is not already closed), a circuit for tip relay TIP isestablished traced from ground through the winding thereof, altematecontact 139, normal contact 1.53, wiper 114, terminal 117, called line,

and substation II, terminal 116, wiper 113,

colltlllctOl' 137, alternate contact 138 and impedance 135 to battery.Relay TIP is therefore energized, closing its alternate contact 140resulting in the cnergization of closing relay L, which interrupts thecircuit for BI to prevent any further application of ringing current tothe called line. This is brought about in the following manner. Thecircuit for relay CL is traced from battery through the winding thereof,alternate contact 140, alternate contact 132, conductor 126, to groundat alternate contact ,121, and due to the closing of alternate contact131 of CL. a locking circuit therefor is established in shunt ofalternate contact 14:0

' of the receiver at H would cause another siothat relayCL is notdirectly controlled b'y'tip relay TIP. Otherwise the replacing lockingcircuit for RR was established through said alternate contact 1-11 toground thereby placing the release relay RR under control of the calledsubstation. Up to the time of the response of-the called subscriber therelease oflconnector J Was controlled from the calling substation, butupon response of" the called subscriber due to the change of lockingcircuit for R-R the release of connector G is controlled at the calledsubstation H. Also, responsive to energization of closing relay CL, itsalternate contacts 142, 143 are closed, thereby establishing a talkingconnection between the calling and called substations, this circuitbeing traced over the heavily marked primary and, secondary conductors.Talking battery for .the called substation is supplied through tip relayTIP and impedance coil 135 While, talking battery for the callingsubstation is supplied through relay PR. Condensers 145, 144 areinterposed in the talking circuit at first selector E, to preventinterference between the relays controlled over the opposite ends of theconnection.

ReZease.After finishing conversation the subscribers replace theirreceivers upon their respective switch-hooks, this act of the calledsubscriber eflecting the restoration of connector switch G and linecircuit 13 while this act of the calling subscriber effects therestoration of line circuit B, line selector C, first selector E andsecond selector F. y

Assuming that the subscriber at H be the first to replace his receiver,the circuit for .relay TIP is interrupted at the called substationwhcreby the said relay restores and by the interruption of its alternatecontact 141 interrupts the locking circuit for R11 which deiincrgizes.Alternate contact 121 thereof is thereby interrupted efi'ecting the.rcstorati on of relays SW, DR and CL, these relays having been heldenergized over locking circuits including this alternate contact 121.Due to the interruption of alternate contact 128 of relay DR, thecircuit for relays RC and CO is interrupted allowing restoration ofthese relays.

Vpon restoration of HR due to the closing of its normal contact 121,ground is connected through alternate contact 147 to test contacts 93rendering them busy during restoration of switch G. Also, uponrestoration of RR, due to the closing of its normal g ntact 148, arelease circuit for secondary magnet 'S1l1' isestablished, traced fromground at alternate contact 11-9 of switch POX, normal Contact 148,overrun contact ()R,interrupter15(lfand the winding of SM to battery.Magnet SM thereupon steps the wipers of switch (1: in a secondarydirection until they have reached a point beyond the last contact in thegroup, whereupon overrun contact OR is interrupted stopping theoperation of magnet SM. Also upon the wipers reaching this point theyare automatically restored by spring tension as previously described.Responsive. to restoration of the switch all off-normal contact sets arerestored.

Responsive to the replacing of the re cciver calling substation A, thecircuit for relay PR is interrupted causing its restoration and due tothe interruption of its alternate contact (34., main release relay MR-R,and release relay RR of line selector C are restored, as it will beremembered that both of these relays have been maintained energized overa circuit including this alternate contact (31.

Referring first to the restoration of switch C, and line switch B, uponrestoration of relay RR, its normal contact 150 is closed establishingan energizing circuit for relays SSH and 151 in series, the circuittherefor being traced from battery through the winding of SSR, contact()R, Winding of 151, normal contact 150, alternate contact 48, andnormal contact 43 to ground. Relay 151 energizes and due to theinterruption of its normal contacts (30, 61, a circuit through windings22 and 58 of relays ST and GR respectively is prevented, althoughalternate contacts 55, 56 of relay SSR are closed. The interruption ofnormal contact 23 of relay 151, interrupts the locking circuit forcut-oil relay CO, causing its deencrgization and restoring control ofline circuit B to substation A, also disconnecting the busy'potentialfrom test terminals 29. Responsive to said energization of relay SSR,and due to the closing of its alternate contact 51, magnet SM advancesthe Wipers of switch C to a point beyond the last contact in the bankwhereby they are automatically restored in a manner as previouslydescribed. Upon the Wipers reaching this o'verrun point, that is a pointbeyond the group, contact OR is interrupted effecting restoration ofrelays 151 and SSH, the

vnormal contact 158 to ground.

contact 99 of TR is thereby closed causing restoration SSH interruptingthe circuit for magnet SM Responsive to restoration of switch C, itsthree off normal contact sets are also restored. the restoration ofnormal contact 45 of PON, removing the ground or busy otential from itsmaster switch contact 1 so far as switch C is concerned, but it will benoted that this contact is main tained busy over conductor 76 toalternate contact 75 until first selector E is restored.

Referring now to first selector E. responsive to restoration of relayMFR. the clos' ing of its normal contact 67 establishes an energizingcircuit for relay. TR traced from said ground at normal contact 67,contact 0R alternatecontact 153, and the winding of TR to batterycausing its energization whereby the closing of its alternate contact81. establishes an operating circuit for secondary magnet SM. The wipersof switch E are then stepped to a point beyond the last contact in therow and from there automatically restored by spring tension in a manneras previously described. Upon interruption of over-run contact OR, thecircuit for relay TB is interrupted caus ing its restortation andpreventing any further operation of magnet SM. The restoration of switchE effects the restoration 'of the off-normal contact sets and uponinterruption of alternate contact 75 of PQN ,v

the ground is disconnected from its test contact 17 at master switch D,and switches C and E being at normal and the ground or bus potentialhaving been removed from their test contact 17 they are now selectableand available for use in establishing other connections. Now as torestoration of second selector F. at the time relay MRR restored as justdescribed, due to the interruption of its alternate contact 83, thelocking circuit forrelay RR of switch F is interru ted causingrestoration of said relay 111 whereby circuit for relay TB isestablished from battery through the winding of TR*, contactORHalternate contact 157, Alternate the releasing operation of secondarymagnet SM. whereby the Wipers are stepped beyond the last contact in therow and from there automatically restored by spring tension in themanner as previously described. Over run contacts OR are operated as inthe case of the other s'witches,-interrupting the circuit for TR whichrestores and interrupts the circuit for magnet SM Second selector Fhaving been restored to normal is available for use in establishingother connections. i

Called line bump-Assuming now that the connection has been extended tothe terminals of a busy called line, test terminal 115 thereof will havea-busy or grounded potential connected thereto, so that'when line testup through its alternate contact 127, and

although its alternate contact 128 is closed as before due to ithefailure of relay LT to retract and close its normal contact 129, ringingcontrol relay RC is not energized. Therefore ringing; current is notapplied to the terminals of the called line. and relay LT beingmaintained energized, by the closure of its alternate contacts 160 acharacteristic busy signal is transmitted to the calling substationtraced from busy back BB, alternate contact 160, back over the lowerheavily marked secondary conductor, out over line conductor 4, receiverof substation A, returning over conductdr 5 along the upper heavilymarked primary conductor and through the upper winding 57 of relay PR,to ground, this-signal indicating to the subscriber at substation A thatthe called line is busy. I Referring to connector G,' it will be notedthat release relay 3R is still controlled from second selector It or infact from the calling substation, so that due to the failure to makeconnection with an idle line and to receive a response thereorer, therelease of connector switch G is controlled at the calling substation.'2 7 I The subscriber at A in response to the signal received, replacesthe receiveruzpon its switch-hook whereby the circuit for relay PR isinterrupted causing its deinergization and the consequent restoration ofre; lease relays MRR and RR as before. 7

The restoration, of relay'BK. causes a restoration of line selector Cand line Citcuit B as before and the restoration 'ofMRR' eli'ects therestoration of first selector E and second selector F as before.

In the present case connector G is. also to be restored, this beingeffected res onsive to the restoration of release relay R of selector Fwhereby the interruption of its alternate contact 101 interrupts thelocking circuit of release relay BB of connector G. whereby it restoresclosing itsnormal contact 148 and establishing a release cir-' lVhat Iclaim as new and desireto secure by Letters Patent is 1. A telephonesystem comprising a group of lines, line selectors for said lines, amaster switch for said selectors, a differential starting relay for saidmaster switch, means for closing an energizing circuit through one ofits windings upon init'ation of a call, whereby an idle line select r isstarted, a primary relay, and means for including a winding of saidprimary relay in circuit with the other winding of said difierentialrelay during the selecting operation of said selector to neutralize saiddifferential relay.

2. A telephone system comprising a group of telephone lines, lineselectors, said lines being divided into sub-groups and multipled tocorresponding sub-groups of contacts of said selectors, a master switch,a differential starting relay for said master switch, a differentialgroup relay for each sub-group of lines, means efl ective uponinitiation of a call over one ,of said lines to close a circuit throughone of the windings of said starting relay and'a winding of thecorresponding group relay, means for start ing an idle one of said lineselectors responsive to said starting relay, a double wound primaryrelay, means for connecting one of the windings thereof in circuit withthe other winding of the said group relay upon selection made with thesub-group of the calling line whereby said group relay is deenergized torender said sub-group nonselectable and means for closing the otherprimary winding in circuit with the other winding of the s arting relayto, render said starting relay inefi'ective.

3. A selector switch including bank contacts divided into groups, acoiiperating wiper, a primary magnet, a secondary magnet, suitablecircuits adapted to cause the operation of said primary magnet to selecta group, suitable circuits to cause said secondary magnet to select a.contact in the group, suitable circuits adapted to cause said secondarymagnet to advance the wiper beyond the last contact of the selectedgroup whereby said wiper is automatically restored, and means forautomatically interrupting the releaseoperation of said secondary magnetupon said wiper being ad' vanced beyond said group.

4. A selector switch comprising groups of bank contacts and acooperating wiper, primary and secondary magnets with suitable circuitarrangements for causing said magnet to advance the wiper to a group andthen to a contact in a group, means when a release is desired to causesaid secondary magnet to advance the wipers beyond the last contact ofthe selected group whereby said wipers automatically restore, and anover-run contact included in the release circuit for rendering saidsecondary magnet inert upon said wiper being advanced be yond said lastcontact.

5. A telephone system comprlsing telea set of terminals in the group, acommon" or group contact for each said group, means responsive to theinitiation of a call in one of said lines for altering the electricalcondition of its group contact to cause selection of its group, meansoperative upon selection of said group contact to render itunselectable, a directively operable selective switch connected to saidline selector, and means responsive to the transmission of impulses overthe two sides of the calling line in series for operating said lastswitch to extend the circuit of the calling line.

6. A telephone system comprising telephone lines, line selectors havingmultiply connected terminal contacts for said lines arranged in groups,said line selectors being adapted for selecting a group and then a setof terminals in the group, multiply connected common or group contactsone for each group at each selector, means responsive to a call in oneof said lines for altering the electrical condition of itscorrespondinggroup contacts and to cause one of said selectors to selectthe corresponding group, means operative upon selection of said group torender its multiply connected group contacts unselectable, a directivelyoperable selective switch associated with each line selector, and meansresponsive to the transmission of impulses over the two sides of thecalling line in series for operating the associated selective switch toextend the circuit of the calling line. I

7. A telephone system comprising telephone lines, line selectors havingmultiply connected terminal contacts for said lines arranged in groups,said line selectors being adapted for selecting a group and then a setof terminals in the group, means responsive to a call in one of saidlines to cause one of said selectors to select the group correspondingto the calling line, means operative by said selection to render themultiply connected groups of the selected group non selectable, meansfor thereafter rendering said multiply connected groups selectable, aselector switch associated with each line selector, and means responsiveto the transmission of impulses over the two sides of the calling linein series for operating the associated selective switch to extend thecircuit of the calling line.

a 8. A telephone system comprising telephone lines, line selectorshaving multiply connected terminal contacts for said lines arranged ingroups, said line selectors being adapted for selecting a group and thena set of terminals in the group, means responsive to a call in one ofsaid lines to cause one of said selectors to select the correspondinggroup of the calling line, means operatlve nected groups ofthe selectedgroupnon-selectable, means responsive to the selection of the callingline terminal contacts to render the associated groups selectable, adirectively operable selective switch associated with each lineselector, and means respon-.

sive to the transmission of impulses over 'the two sides of the callingline in series for operating the associated selective switch to extendthe circuit of the calling line.

9. A selector switch including bank contacts arranged in rows, acoiiperating wiper therefor, a primary magnet and a secondary magnet forsaid switch, means for operating said primary magnet to select one ofsaidrows, means for operating said secondary magnet to select a contactin the selected row, means for afterward operating the secondary magnetto advance the wiper beyond the'last contact in the said selectedgroupiwhereby said wiper is automatically restored, and means forautomatically interrupting the release operation of the secondary magnetupon the wiper advancing past the last contact of said group.

groups, means for. operating said second ary magnet to cause a selectionof a contact in the selected. group, suitable circuits adapted to causesaid secondary magnetto advance the wiper beyond the last contact of theselected group whereby said wiper is automatically restored, and meansfor automatically interrupting the operation of said secondary magnetwhen said wiper is advanced beyond said group.

12. A selector switch comprising groups of bank contacts and acooperating wiper,

primary circuits for advancing the wiper to a group and then to acontact in av group, means when release is desired to cause said secondary magnet to advance the wiper beyond the last contact of the selectedgroup whereby said wiper automatically restores, and an over-run contactincluded in the release circuit of the secondary magnet for renderingsaid secondary magnet inert upon. the said wiper being advanced beyondsaid last contact.

13. A telephone system comprising telephone lines, a line selectorhaving terminals 10. In a telephone system the combina-e for said linesarranged in groups. electrotion with contacts arranged in groups, a lineselector for selecting a group and for then selecting a contact in thegroup, a common contact for each group, means for altering theelectrical. condition of one of said common contacts to cause selectionof its group by the selector, means responsive to the initial travel ofthe selector to select a contact in the selected group to render thesaid common contact unselectable, a directively operable selectiveswitch connected to said line selector, and means responsive to thetransmission of impulses over the two sides of the calling line inseries for operating said last mentioned switch to extend the circuit ofthelcalling line.

11. A selector switch including bank contacts divided into groups, acooperating wiper, a primary'-'magnet and a-secondary magnet, means foroperating said primary magnet to cause a selectionfof one of s aid andsecondary .magnets,- suitable,

operative upon such selection to render said group contact unselectable,a directively operable selective switch connected to said line selector,and means for controlling the operation of said switch over the twosides of the calling line in series. I

Signed by me at New York, county of New York and State of New York inthepresence of two witnesses.

ALFRED DYSON.

Witnesses:

C. F. BALDWIN, K. B. DOHERTY.

